Wound inductor coil form



Feb. 6, 1968 R. H. HILGERS wounn INDUGTOR coIL. FORM Filed June 7, 1966INVENTOR: RAYYMOND H. HILGERS ATT'YS f) at United States Patent D3,368,177 WOUND INDUCTOR COIL FORM Raymond H. Hilgers, Roselle, 11].,assign-or to Resinite Corporation, Wheeling, 111., a corporation ofIllinois Filed June 7, 1966, Ser. No. 555,776 6 Claims. (Cl. 336-203)ABSTRACT OF THE DISCLQSURE A coil form for supporting an electricalwinding. The coil form comprises an elongated tubular body provided witha plurality of circumferentially spaced longitudinally extendingrecesses in the outer wall thereof. The recesses define thin webportions which connect relatively thick portions adjacent each recess,and each web portion is provided with an interiorly projecting web forengagement with a core. The outer surface of the web portions are spacedfrom the outer surfaces of the thick portions to permit outward flexureof the web portions.

This invent-ion relates to a coil form, and, more particularly, to atubular element adapted to be incorporated into electronic apparatus asan inductor.

Exemplary of the use of the invention is in connection with IF coilsused in radio and television receivers. These require adjustment bymeans of positioning a core within the tubular coil form. Such cores areusually constructed of powdered iron and are quite delicate, i.e.,frangible. Over the years, various expedients have been employed forproperly sup-porting the cores within the tubular coil forms. Mostcommonly, the coil forms are equipped with female threads to receive thecores at various positions so as to change the inductive value of thecoil. It will be appreciated that the inductive value is not onlygoverned by the position of the core, but also by the configuration,i.e., total geometry, of the windings. This places a distinct limitationon the character of coil forms heretofore employed. I find that thislimitation is overcome and avoided through a novel construction makinguse of circumferentially spaced resilient web portions, and theprovision of such a coil form constitutes an important objective of thisinvention.

Other objects and advantages of the invention may be seen in the detailsof construction and operation set down in this specification.

The invention is described in conjunction with an illustrativeembodiment in the accompanying drawing, in which:

FIG. 1 is a perspective view of a coil form constructed according tothis invention;

FIGv 2 is an enlarged transverse sectional view taken along the line 22of FIG. 1; and

FIG. 3 is a view similar to FIG. 2, but showing a core installed inplace in the form and wherein the form is equipped with the usualwindings.

In the illustration given and with particular reference to FIG. 1, thenumeral designates generally the inventive coil form which is seen toinclude a unitary body equipped with a perimetric flange 11 adjacent oneend and which constitutes a stop for mounting the form on a chassis orother electronic gear-supporting frame. Advantageously, the body 10 isconstructed of substantially rigid plastic material having resilientproperties such as unplasticized polyethylene and which is an electricalinsulator.

Extending generally from the vicinity of the perimetric flange 11 are aplurality of longitudinally-elongated recesses 12 which are seen toextend from the outer surface of the coil form body 10 into the bodyproper and which 3,358,177 Patented Feb. 6, 1968 define web or bightportions 13. The web portions 12 are flanked by shoulders 14 whichextend generally at about 45 to a median radius 15, so as to define theangle as indicated on the drawing. -In addition, each web is equippedwith longitudinally-extending rib portions projecting inwardly of thetubular coil form as at 16.

In operation, when the core 17 (see FIG. 3) is installed, there is alimited flexure of the relatively thin and, therefore, slightlyresilient web portions 13, as indicated in FIG. 3, so as to move thesame into the recesses 12, but without disturbing the overall geometryof the coil form which is important in governing the inductance of thevarious windings 18. This is particularly advantageous in that thethreads of the powdered iron core 17 do not have to cut into the rib 16.It will be appreciated that such cores are quite frangible and a slightexcess of torque can cause rupture. The partial destruction of a corecan result in a change in the inductance of the coil achieved byover-winding the form 10 as at 18.

The molded coil form of the invention is particularly advantageous inreducing the amount of torque needed to insert the core 18. Here, itwill be appreciated that the core is inserted into the form 10 from theend 19 (see FIG. 1) while the form 10 is supported at the end designated20. For this purpose, the unitary member 10 is equipped with integrallongitudinal-extending flanges as at 21 separated by slots 22 whichaccommodate the mounting of the coil form 10 by permitting the same tobe snapped onto a chassis (not shown).

A specific example of the invention for use with a core having a nominaldiameter (O.D. of the thread) of 0.248" and an ID. of the undistortedform (see FIG. 2) of 0.254". The diameter between opposed ribs 16 is0.232", resulting in inwardly-extending ribs of the order of0.008"-0.0l2". The thickness of the bight or web portion 13- is of theorder of 0008" resulting in an outside diameter between exteriors of thebight portions of 0.270. Finally, the dimension A in the illustrationgiven wherein there are four recesses at 12, is 0.160".

While in the foregoing specification, a detailed description of anembodiment of the invention has been set down for the purpose ofillustration, many variations in the details herein given may be made bythose skilled in the art without departing from the scope of theinvention.

I claim:

1. A coil form for supporting an electrical winding, com-prising arelatively elongated unitary tubular body constructed ofnon-electrically conductive material having resilient properties, aplurality of circumferent-ially spaced-apart, longitudinally-extendingrecesses in the outer wall of said form defining relatively thin andrelatively flexible web portions interconnecting relatively thick andrelatively rigid portions adjacent each recess, said web portions beingsubstantially thinner than said thick portions, each web portion beingequipped with an interiorly projecting, longitudinally-extendingintegral rib for engagement with a threaded core whereby the web portionis adapted to selectively flex to accommodate said core.

2. The structure of claim 1 wherein said recesses terminate short of theends of said body.

3. The structure of claim 1 in which said recesses are defined andflanked by shoulders arranged at about 45 angles relative to a medianradius extending through an associated rib.

4. An electrical inductance comprising a coil form having a relativelyelongated unitary tubular body constructed of non-electricallyconductive material having resilient properties, a plurality ofcircumferentially spacedapart, longitudinally extending recesses in theouter wall of said form defining relatively thin web portionsinterconnecting relatively thick portions adjacent each recess,

each web portion being equipped with an interiorly projecting,longitudinally extending integral web for engagement with a threadedcore, a winding on said form supported by said thick portions and spacedfrom said web portions, whereby the web portion is adapted toselectively flex to accommodate a core.

5. The structure of claim 4 in which said recesses terminate short ofthe end of said body.

6. The structure of claim 4 in which said recesses are defined andflanked by shoulders arranged at about a 45 angle relative to a medianradius extending through an associated web.

References Cited UNITED STATES PATENTS 2,328,335 2,631,192 3/1953 Wallin336-136 X 3,129,348 7/1964 Simmons 242-418 FOREIGN PATENTS 866,952 4/1961 Great Britain,

10 LARAMIE E. ASK'IN, Primary Examiner.

E. GOLDBERG, Assistant Examiner.

8/1943 Fryer 2421l8.2

